Liquid crystal display devices use a backlight unit for radiating light from behind the liquid crystal display panel to illuminate the liquid crystal display panel. A backlight unit is configured using a light guide plate for diffusing light emitted by an illuminating light source to irradiate the liquid crystal display panel and parts such as a prism sheet and a diffusion sheet for rendering the light emitted from the light guide plate uniform.
Currently, large liquid crystal televisions predominantly use a so-called direct illumination type backlight unit comprising a light guide plate disposed immediately above the illuminating light source (see, for example, JP 05-4133 U). This type of backlight unit comprises a plurality of cold cathode tubes serving as a light source provided behind the liquid crystal display panel whereas the inside of the backlight unit provides white reflection surfaces to ensure uniform light amount distribution and necessary brightness.
To achieve a uniform light amount distribution with a direct illumination type backlight unit, however, a thickness of about 30 mm in a direction perpendicular to the liquid crystal display panel is required. While demands of still thinner backlight units are expected to grow in the future, achieving a thickness of 10 mm or less with a direct illumination type backlight unit is deemed difficult in view of uneven light amount distribution expected to accompany that type.
Against such background, there is provided a tandem type as a thin backlight unit (see, for example, JP 02-208631 A, JP 11-288611 A, and JP 2001-312916 A).
[PATENT DOCUMENT 1]: JP 05-4133 U
[PATENT DOCUMENT 2]: JP 02-208631 A
[PATENT DOCUMENT 3]: JP 11-288611 A
[PATENT DOCUMENT 4]: JP 2001-312916 A